Generally, an input device using a touch screen method, also referred to as a glass touch method, allows a user to selectively touch a certain region of a surface of the input device to input a command. Such input device using the glass touch method has been widely used as a device for inputting commands of users in advanced electric home appliances and electronic goods such as microwave ovens, display screens, and televisions.
As shown in FIG. 1, a well-known input device using the glass touch method includes a key matrix 10 configured with N×N number of glass touch sensors, a key control unit 20 outputting a scan input signal to the key matrix 10 and receiving a scan output signal outputted from the key matrix 10 when a contact of a human body or an object occurs, and a micro computer 30 outputting the scan input signal of the key matrix 10 and receiving the scan output signal of the key matrix 10 by a parallel data communication with the key control unit 20. Herein, the key matrix 10 and the key control unit 20, which is a touch sensor chip, configure a set. The key matrix 10 and the key control unit 20 that processes signals of the key matrix 10 are applied together in order to be applied as an input device in a certain product.
An operation of an input device according to such configuration is as follows.
The micro computer 30 outputs a scan input signal to the key control unit 20 to sense a key signal of the key matrix 10. The key control unit 20 transfers the scan input signal outputted from the micro computer 30 to the key matrix 10 according to its own logic. The logic may be a form of controlling a sequence of input signals.
At this time, when a user touches a certain position of the key matrix 10, capacitance of the glass touch sensor corresponding to the outputted scan input signal section becomes variable and an electrical signal is outputted.
The key signal outputted from the key matrix 10 is transferred into a scan output signal port of the micro computer 30 via the key control unit 20, and the micro computer 30 recognizes the inputted scan output signal as the corresponding key signal.
The micro computer 30 is formed to execute a parallel communication method with the key control unit 20 to recognize the key signal of the key matrix 10. The micro computer 30 is generally required to have a scan input signal port and a scan output signal port with respect to the key matrix 10. In FIG. 1, a region ‘A’ shows scan input signals and scan output signals being exchanged between the micro computer 30 and the key control unit 20. The region ‘A’ executes the parallel communication method.
For instance, if the key matrix 10 is configured with 16 keys (4×4), the micro computer 30 requires 4 scan input signal ports and 4 scan output signal ports. That is, the key control unit 20 and the micro computer 30 need a total of 8 data connecting ports connected for inputting and outputting of scan signals.
Recently, more number of keys has been demanded as functions of electric home appliances and electronic goods have become diversified. According to the conventional method, a key matrix demanded by a product has to be constructed from 1, 2, 4, or 16 keys. If 64 keys are demanded, 4 sets of key matrixes configured with 16 keys (4×4) are required. Also, since the micro computer 30 and the key control unit 20 have to be connected in parallel, each set requires 8 data connecting ports, that is, 32 data connecting ports in total. Thus, a micro computer with advanced specification is required and the connection process is difficult. That is, since the micro computer and the key control unit including many data connecting ports are demanded according to the number of keys, product cost is increased and the embodiment of the input device becomes complicated and difficult.
Furthermore, because the glass touch sensor is a key sensor of a capacitance method, a noise may be generated by capacitance interferences between sets while processing key signals when more than two sets of key matrixes are formed. Thus, a key error may be generated.
Moreover, when more than two set of key matrixes are formed, carelessly pressing a key matrix provided at a border portion of the key matrix of a set may cause touching a key pattern at a border portion of another set of key matrix. Thus, interferences may be generated in-between.
Also, as the number of sets of key matrixes is increasing, processing loads of the micro computer increase to result in high chances of errors. Unlike the micro computer, the key control unit has a low efficiency because resources of the key control unit are not adequately used despite the abundance.